When one of the hostages asks for "insulin", the professor includes it in the list of medicines requested to the negotiation squad. Diabetic treatment requires an indication of the type of insulin the patient is prescribed (like rapid, short, or intermediate-acting) and how it is applied (pump, injection, or pen). You cannot merely ask for "insulin".
When Berlín threatens Moscú with his Colt M1911-A1, in the close-up of the gun you can clearly see the "Reck" brand name on it, revealing the gun to be a blank firing replica. The Reck Colt M1911-A1 hasn't been built since the turn of the millennium and most specimens in circulation look very much used, which makes them perfect movie props. Later, when Denver puts his gun in Arturo Román's mouth, the labeling "9mm P.A.K." - a blank caliber - is also clearly visible on the gun.